techlayer/espresso.js — pull request #1 by JacobJWBurden (2014-11-11 22:52:05+00:00)
Title: Better isXXX by checking [[Class]] with toString

I think it may help to follow the path lead from other projects such as underscore, since this awesome lightweight framework is inspired by Backbone. It seems this implementation is faster on modern browsers as well. http://jsperf.com/underscore-js-istype-alternatives